There is a lack of detailed information on the role of substance use disorders (SUD) as a substantial factor in offences and treatment in forensic psychiatric patients. The aim of this study was to get a better understanding of these specifics. Clinical records of 193 male patients admitted to a Dutch forensic psychiatric hospital were scrutinized on anamnestic, diagnostic and risk assessment data. One of the central findings was that the prevalence of SUDs was high. Patients with an SUD had a more extensive criminal history, unstable and deviant lifestyle and higher risk of violent behavior than patients without a substance use disorder. No differences were found in duration of treatment, aggressive incidents and leave. Another important finding was that a distinction could be made between patients with substance use as a primary criminogenic risk factor and patients with substance use as a secondary risk factor. Although substance use is identified as a general risk factor, this study supports the idea of sub categorization of patients with an SUD and emphasizes the need for a different treatment approach. Further study is needed to identify specific treatment approaches, based on more differentiated profiles of these patients.